In a typical CMOS random access memory formed in an integrated circuit the normal and complementary outputs of an addressed data storage element to be read are connected to normal and complementary output conductors of which one is discharged from a voltage level to which both were previously charged, which conductor is discharged depending on whether the bit stored in the addressed element is a "1" or a "0". The rate of discharge is relatively slow and therefore to speed up the establishment of voltages representing the stored bit on the conductors a pair of transistors is provided, each discharging one conductor at a rate depending on the voltage on the other conductor, thereby causing the conductor having the lower voltage to be discharged more quickly than that having the higher voltage. Thus the output conductors rapidly assume distinct voltages corresponding to the bit stored in the addressed element. It is, however, important that the cross-connected pair of transistors is not switched into circuit before a certain minimum difference between the voltages on the conductors has been set up by the addressed storage element, otherwise there would be a risk that the final voltages on the conductors did not clearly and accurately represent the bit from the addressed storage element. To this end, the current paths through the pair of transistors are commoned and passed through a further transistor the conductivity of which is controlled by a sense clock signal, the timing of which is controlled to permit at least the required minimum difference between the conductor voltages to be set up before the cross-connected pair of transistors become effective. The invention is concerned with the timing of the sense clock signal which must not be too early to avoid corruption of the data and if it is unnecessarily late it will undesirably increase the access time of the memory.
It is an object of the present invention to overcome the above difficulty.